1. Field of the Invention
The invention relates to a light-emitting diode (LED) illumination apparatus and particularly to an LED illumination apparatus having favorable efficiency in heat dissipation.
2. Description of Related Art
A light-emitting diode (LED) is a semiconductor element, and the material for forming a light-emitting chip of an LED mainly includes chemical elements selected from groups III-V, such as gallium phosphide (GaP), gallium arsenide (GaAs), and other compound semiconductors. The light-emitting principle is converting electric energy into light, namely applying electric current to a compound semiconductor, so that redundant energy is released in the form of light through the combination of electrons and electron holes, thereby achieving light-emitting effects. Since the light-emitting phenomenon of LED is not caused by heating or discharging, the lifespan of LED is more than 100,000 hours, and idling time is saved. Moreover, LED has the advantages of quick response speed (about 10−9 seconds), compact size, low power consumption, low pollution, high reliability, capability for mass production, etc. Therefore, the application of LED is fairly extensive, for example, mega-size outdoor display boards, traffic lights, cell phones, light sources of scanners, illumination devices, and so forth.
In recent years, as the brightness and light-emitting efficiency of LED are being improved and the mass production of white light LEDs is carried out successfully, white light LEDs are used in illumination devices increasingly, such as indoor illuminators, outdoor illuminators and so forth. Generally speaking, high-power LEDs all encounter heat dissipation problems. When an LED is operated in an overly high temperature, the brightness of the LED illumination apparatus may be reduced and the lifespan of the LED may be shortened. Therefore, how to design a proper heat dissipation system for LED illumination apparatuses has become a focus to researchers and designers in this field. According to the design of the heat dissipation system of a conventional LED illumination apparatus, the light source and the power supply are operated in nearly the same temperature. However, the optimal operation temperatures for the light source and the power supply are different. The conventional heat dissipation design cannot provide optimal temperatures for the light source and the power supply to operate. Consequently, the lifespan of the LED illumination apparatus is affected.